The diagnosis of kidney disorders is classically based on the presence of one or more signs and symptoms. For example, signs and symptoms of acute renal failure, renal tubular injury, renal cancer or glomerulonephritis may include weight gain, reduced urine output, increased serum creatine concentrations, hypertension, fever, and kidney enlargement and tenderness. However, the use of these signs and symptoms alone to detect kidney disorders is not adequate. Currently, most kidney disorders are diagnosed by measuring kidney function, for example by using biochemical tests such as assays that measure serum creatinine (Cr) concentrations, and by imaging or biopsy.
Presently, renal biopsy remains the most definitive test to specifically diagnose many kidney disorders. However, renal biopsy has major limitations. For example, the biopsy procedure itself has complications, and cannot be performed on a routine or serial basis to monitor progression of renal disease. In addition, a renal biopsy is invasive, making it uncomfortable, inconvenient and often dangerous for patients. Moreover, accurate interpretation of a renal biopsy demands the expertise of a pathologist with extensive experience in analyzing the sample for evidence of specific kidney disorders. Hence, renal biopsies are reserved for those patients demonstrating other clinical and/or laboratory evidence of a kidney disorders, thus limiting its broader use.
Thus, a less invasive method for the diagnosis, prediction and monitoring of kidney disorder is clearly needed.